Challenges on Drilling Operations of Deep Wells in Ultradeepwater Zones in the Gulf of Mexico

Abstract

Abstract Currently some of the most challenging wells being drilled by our industry are located in deepwater zones in the GOM. Many of those wells are in water depths of 8,000 ft. or more and several are targeting reservoirs around 30,000 ft. and beyond. Drilling engineers face many challenges when planning drilling and completion operations for such wells. There are not many rigs available to drill in ultra-deepwater, and even the modern rigs capable of operating in this environment will present limitations ranging from the maximum mud weight possible to be used, due to riser restrictions, to the hook load capability to run very heavy intermediate casings that will easily surpass one million pounds. The well itself will present many problems including high pressure and high temperature formations, the need of multiple casing strings, unstable formations, hole cleaning, unexpected presence of tar zones, huge layers of salt, the need to underream the well, difficult to do an efficient evaluation program etc. On the completion side, the challenges can be even more demanding, with the need to complete multiple zones while trying to minimize future expensive workover operations. This paper presents some practical experiences on dealing with various of the abovementioned problems and also suggestions to make the problems manageable. It might be emphasized that we do not have a perfect solution to all problems and that we are far to have the most efficient solution to drill deep wells located in ultra-deepwater zones in the GOM. However, with daily operational costs reaching one million dollars or more, it is our intention in this paper to discuss the problems, to point out some possible directions, to show some field cases and to open a discussion that might benefit the entire industry. Introduction Many are the challenges to develop newly discovered accumulations in deepwater Gulf of Mexico. Exploration, appraisal and production drilling in areas such as Mississippi Canyon, Atwater Valley, Walker Ridge, Keathley Canyon and others (Fig. 1) present, besides the inherent difficulties associated with deepwater drilling, very deep interest zones which demand careful planning to be reached without compromising safety, well integrity, formation evaluation and estimated budget. Furthermore, challenges will remain in case of geologic success and may even increase with the difficult to find an ideal seafloor location to place the production wells drilling center. This may be a complex task due to shallow hazards or seafloor configuration.